Propylene copolymer compositions having a good low-temperature impact toughness and a high transparency

ABSTRACT

The present invention relates to a propylene copolymer composition comprising A) a propylene polymer containing from 0 to 10% by weight of olefins other than propylene and B) at least one propylene copolymer containing from 5 to 40% by weight of olefins other than propylene, where the propylene polymer A and the propylene copolymer B are present as separate phases and the propylene copolymer composition has a haze value of ≦30%, based on a path length of the propylene copolymer composition of 1 mm, and the brittle/tough transition temperature of the propylene copolymer composition is ≦−15° C.

The invention relates to propylene copolymer compositions, to a processfor producing the propylene copolymer compositions, to the use of thepropylene copolymer compositions of the present invention for producingfibers, films or moldings and also to fibers, films or moldingscomprising the propylene copolymer compositions of the presentinvention.

Propylene polymers are one of the classes of plastics most frequentlyused today. The customarily used polymers of propylene have an isotacticstructure. They can be processed to form shaped bodies which possessadvantageous mechanical properties, especially a high hardness,stiffness and shape stability. Consumer articles made of propylenepolymers are used in a wide range of applications, e.g. as plasticcontainers, as household or office articles, toys or laboratoryrequisites. However, the products known from the prior art do not havethe combination of low-temperature impact toughness together with a goodtransparency and good stress whitening behavior required for manyapplications.

It is known that multiphase propylene copolymers having a good impacttoughness, particularly at low temperatures, can be prepared by means ofZiegler-Natta catalyst systems in a multistage polymerization reaction.However, the incorporation of ethylene-propylene copolymers having ahigh proportion of ethylene into a polymer matrix, which is necessary toincrease the low-temperature impact toughness, makes the multiphasepropylene copolymer turbid. Poor miscibility of the flexible phase withthe polymer matrix leads to a separation of the phases and thus toturbidity and to poor transparency values of the heterogeneouscopolymer. Furthermore, the ethylene-propylene rubber prepared by meansof conventional Ziegler-Natta catalysts also has a very inhomogeneouscomposition.

It is also known that multiphase copolymers of propylene can be preparedusing metallocene catalyst systems. Propylene polymers prepared usingmetallocene catalyst systems have low extractable contents, ahomogeneous comonomer distribution and good organoleptics.

The multiphase copolymers of propylene disclosed in WO 94/28042 have thedisadvantage that they have a melting point which is too low, which hasan adverse effect on the stiffness and the heat distortion resistance ofthe copolymers. Furthermore, the toughness, too, is not yetsatisfactory.

EP-A 433 986 describes multiphase propylene copolymers having asyndiotactic structure which were obtained using specific metallocenecatalyst systems. These propylene copolymer compositions have relativelylow melting points and consequently a low stiffness and a low heatdistortion resistance.

EP-A 1 002 814 describes multiphase copolymers of propylene whichdisplay an excellent balance between stiffness, impact toughness andheat distortion resistance.

WO 01/48034 relates to metallocene compounds by means of which propylenecopolymers having a high molar mass and a high copolymerized ethylenecontent can be obtained under industrially relevant polymerizationconditions. Multiphase propylene copolymers having a highstiffness/impact toughness level are obtainable in this way.

However, the multiphase propylene copolymers disclosed in the prior arthave the disadvantage that a satisfactory combination of low-temperatureimpact toughness with a good transparency and at the same time goodstress whitening behavior has not been achieved. The products eitherhave a not yet satisfactory impact toughness at low temperatures or havestill unsatisfactory values for transparency and stress whitening.

It is an object of the present invention to overcome the above-describeddisadvantages of the prior art and to provide propylene copolymercompositions which have a combination of good impact toughness at lowtemperatures together with good transparency and good stress whiteningbehavior and also possess a relatively high melting point, a highstiffness and good heat distortion resistance in combination with lowextractable contents, a homogeneous comonomer distribution and goodorganoleptics.

We have found that this object is achieved by propylene copolymercompositions comprising

-   A) a propylene polymer containing from 0 to 10% by weight of olefins    other than propylene and-   B) at least one propylene copolymer containing from 5 to 40% by    weight of olefins other than propylene,    where the propylene polymer A and the propylene copolymer B are    present as separate phases and    the propylene copolymer compositions have a haze value of ≦30%,    based on a path length of the propylene copolymer composition of 1    mm and the brittle/tough transition temperature of the propylene    copolymer compositions is ≦−15° C.

Furthermore, we have found a process for preparing propylene copolymercompositions, the use of the propylene copolymer compositions forproducing fibers, films or moldings and also fibers, films or moldingswhich comprise propylene copolymer compositions of the presentinvention, preferably as substantial component.

The propylene polymer A present in the propylene copolymer compositionsof the present invention and the propylene copolymer present ascomponent B are present as separate phases. Propylene copolymercompositions having such a structure are also referred to as multiphasepropylene copolymers, heterogeneous propylene copolymers or as propyleneblock copolymers.

In the multiphase propylene copolymer compositions of the presentinvention, the propylene polymer A usually forms a three-dimensionallycoherent phase in which the phase of the propylene copolymer B isembedded. Such a coherent phase in which one or more other phases aredispersed is frequently referred to as the matrix. The matrix usuallyalso makes up the major proportion by weight of the polymer composition.

In the multiphase propylene copolymer compositions of the presentinvention, the propylene copolymer B is generally dispersed in finelydivided form in the matrix. Furthermore, the diameter of the thenisolated domains of the propylene copolymer B is usually from 100 nm to1000 nm. Preference is given to a geometry with a length in the rangefrom 100 nm to 1000 nm and a thickness in the range from 100 to 300 nm.The determination of the geometry of the individual phases of thepropylene copolymer compositions can be carried out, for example, byevaluation of contrasted transmission electron micrographs (TEMs).

To prepare the propylene polymers present in the propylene copolymercompositions of the present invention, at least one further olefin isused as monomer in addition to propylene. As comonomers in the propylenecopolymers B and optionally in the propylene polymers A, all olefinsother than propylene, in particular α-olefins, i.e. hydrocarbons havingterminal double bonds, are conceivable. Preferred α-olefins are linearor branched C₂-C₂₀-1-alkenes other than propylene, in particular linearC₂-C₁₀-1-alkenes or branched C₂-C₁₀-1-alkenes, e.g. 4-methyl-1-pentene,conjugated and unconjugated dienes such as 1,3-butadiene, 1,4-hexadieneor 1,7-octadiene or vinylaromatic compounds such as styrene orsubstituted styrene. Suitable olefins also include olefins in which thedouble bond is part of a cyclic structure which may comprise one or morering systems. Examples are cyclopentene, norbornene, tetracyclododeceneor methylnorbornene or dienes such as 5-ethylidene-2-norbornene,norbornadiene or ethylnorbornadiene. It is also possible to copolymerizemixtures of two or more olefins with propylene. Particularly preferredolefins are ethylene and linear C₄-C₁₀-1-alkenes such as 1-butene,1-pentene, 1-hexene, 1-heptene, 1-octene, 1-decene, in particularethylene and/or 1-butene.

The propylene polymer A present in the propylene copolymer compositionsof the present invention may be a propylene homopolymer or a propylenecopolymer containing up to 10% by weight of olefins other thanpropylene. Preferred propylene copolymers contain from 1.5 to 7% byweight, in particular from 2.5 to 5% by weight, of olefins other thanpropylene. As comonomers, preference is given to using ethylene orlinear C₄-C₁₀-1-alkenes or mixtures thereof, in particular ethyleneand/or 1-butene. The propylene polymer A preferably has an isotacticstructure, which hereinafter means that, with the exception of a fewfaults, all methyl side groups are arranged on the same side of thepolymer chain.

The component B present in the propylene copolymer compositions of thepresent invention is made up of at least one propylene copolymercontaining from 5 to 40% by weight of olefins other than propylene. Itis also possible for two or more propylene copolymers which aredifferent from one another to be present as component B; these maydiffer in respect of both the amount and type of the copolymerizedolefin(s) other than propylene. Preferred comonomers are ethylene orlinear C₄-C₁₀-1-alkenes or mixtures thereof, in particular ethyleneand/or 1-butene. In a further, preferred embodiment, monomers containingat least two double bonds, e.g. 1,7-octadiene or 1,9-decadiene, areadditionally used. The content of the olefins other than propylene inthe propylene copolymers is generally from 7 to 25% by weight,preferably from 10 to 20% by weight, particularly preferably from 12 to18% by weight and in particular from 14% by weight to 17% by weight,based on the propylene copolymer B.

The weight ratio of propylene polymer A to propylene copolymer B canvary. It is preferably from 90:10 to 60:40, particularly preferably from80:20 to 60:40 and very particularly preferably from 70:30 to 60:40.Here, propylene copolymer B includes all the propylene copolymersforming the component B.

The propylene copolymer compositions of the present invention have ahaze value of ≦30%, preferably ≦25%, more preferably ≦20%, particularlypreferably ≦15% and very particularly preferably ≦12%, based on a pathlength of the propylene copolymer composition of 1 mm. The haze value isa measure of the turbidity of the material and is thus a parameter whichcharacterizes the transparency of the propylene copolymer compositions.The lower the haze value, the higher the transparency. Furthermore, thehaze value is also dependent on the path length. The thinner the layer,the lower the haze value. The haze value is generally measured inaccordance with the standard ASTM D 1003, with different test specimensbeing able to be used, for example injection-molded test specimenshaving a thickness of 1 mm or films having a thickness of, for example,50 μm. According to the present invention, the propylene copolymercompositions are characterized by means of the haze value ofinjection-molded test specimens having a thickness of 1 mm.

Furthermore, the propylene copolymer compositions of the presentinvention have a brittle/tough transition temperature of ≦−15° C.,preferably ≦−18° C. and particularly preferably ≦−20° C. Very particularpreference is given to brittle/tough transition temperatures of ≦−22°C., in particular ≦−26° C.

Propylene polymers are tough materials at room temperature, i.e. plasticdeformation occurs under mechanical stress only before the materialbreaks. However, at reduced temperatures, propylene polymers displaybrittle fracture, i.e. fracture occurs virtually without deformation orat a high propagation rate. A parameter which describes the temperatureat which the deformation behavior changes from tough to brittle is the“brittle/tough transition temperature”.

In the propylene copolymer compositions of the present invention, thepropylene polymer A is generally present as matrix and the propylenecopolymer B, which usually has a stiffness lower than that of the matrixand acts as impact modifier, is dispersed therein in finely dividedform. Such an impact modifier not only increases the toughness atelevated temperatures but also reduces the brittle/tough transitiontemperature. For the purposes of the present invention, thebrittle/tough transition temperature is determined by means of puncturetests in accordance with ISO 6603-2, in which the temperature is reducedin continuous steps. The force/displacement graphs recorded in thepuncture tests enable conclusions as to the deformation behavior of thetest specimens at the respective temperature to be drawn and thus allowthe brittle/tough transition temperature to be determined. Tocharacterize the specimens according to the present invention, thetemperature is reduced in steps of 2° C. and the brittle/toughtransition temperature is defined as the temperature at which the totaldeformation is at least 25% below the mean total deformation of thepreceding 5 measurements; here, the total deformation is thedisplacement through which the punch has traveled when the force haspassed through a maximum and dropped to 3% of this maximum force. In thecase of specimens which do not display a sharp transition and in whichnone of the measurements meet the specified criterion, the totaldeformation at 23° C. is employed as reference value and thebrittle/tough transition temperature is the temperature at which thetotal deformation is at least 25% below the total deformation at 23° C.

Furthermore, the propylene copolymer compositions of the presentinvention display good stress whitening behavior. For the purposes ofthe present invention, stress whitening is the occurrence of whitishdiscoloration in the stressed region when the polymer is subjected tomechanical stress. In general, it is assumed that the whitediscoloration is caused by small voids being formed in the polymer undermechanical stress. Good stress whitening behavior means that no or onlyvery few regions having a whitish discoloration occur under mechanicalstress.

One method of quantifying stress whitening behavior is to subjectdefined test specimens to a defined impact stress and then to measurethe size of the resulting white spots. Accordingly, in the dome method,a falling dart is dropped onto a test specimen in a falling dartapparatus in accordance with DIN 53443 Part 1. In this method, a fallingdart having a mass of 250 g and a punch of 5 mm in diameter is used. Thedome radius is 25 mm and the drop is 50 cm. The test specimens used areinjection-molded circular disks having a diameter of 60 mm and athickness of 2 mm, and each test specimen is subjected to only oneimpact test. The stress whitening is reported as the diameter of thevisible stress whitening region in mm; the value reported is in eachcase the mean of 5 test specimens and the individual values aredetermined as the mean of the two values in the flow direction oninjection molding and perpendicular thereto on the side of the circulardisk opposite that on which impact occurs.

The propylene copolymer compositions of the present invention display noor only very little stress whitening determined by the dome method at23° C. In the case of preferred propylene copolymer compositions, avalue of from 0 to 8 mm, preferably from 0 to 5 mm and in particularfrom 0 to 2.5 mm, is determined by the dome method at 23° C. Veryparticularly preferred propylene copolymer compositions display nostress whitening at all in the test carried out by the dome method at23° C.

The propylene copolymer compositions of the present invention generallyfurther comprise customary amounts of customary additives known to thoseskilled in the art, e.g. stabilizers, lubricants and mold releaseagents, fillers, nucleating agents, antistatics, plasticizers, dyes,pigments or flame retardants. In general, these are incorporated duringgranulation of the pulverulent product obtained in the polymerization.

Customary stabilizers include antioxidants such as sterically hinderedphenols, processing stabilizers such as phosphites or phosphonites, acidscavengers such as calcium stearate or zinc stearate or dihydrotalcite,sterically hindered amines or UV stabilizers. In general, the propylenecopolymer compositions of the present invention contain one or morestabilizers in amounts of up to 2% by weight.

Suitable lubricants and mold release agents are, for example, fattyacids, calcium or zinc salts of fatty acids, fatty acid amides or lowmolecular weight polyolefin waxes, which are usually used inconcentrations of up to 2% by weight.

Possible fillers are, for example, talc, chalk or glass fibers, andthese are usually used in amounts of up to 50% by weight.

Examples of suitable nucleating agents are inorganic additives such astalc, silica or kaolin, salts of monocarboxylic or polycarboxylic acids,e.g. sodium benzoate or aluminum tert-butylbenzoate,dibenzylidenesorbitol or its C₁-C₈-alkyl-substituted derivatives such asmethyldibenzylidenesorbitol, ethyldibenzylidenesorbitol ordimethyldibenzylidenesorbitol or salts of diesters of phosphoric acid,e.g. sodium 2,2′-methylenebis(4,6,-di-tert-butylphenyl)phosphate. Thenucleating agent content of the propylene copolymer composition isgenerally up to 5% by weight.

Such additives are generally commercially available and are described,for example, in Gächter/Müller, Plastics Additives Handbook, 4thEdition, Hansa Publishers, Munich, 1993.

In a preferred embodiment, the propylene copolymer compositions of thepresent invention contain from 0.1 to 1% by weight, preferably from 0.15to 0.25% by weight, of a nucleating agent, in particulardibenzylidenesorbitol or a dibenzylidenesorbitol derivative,particularly preferably dimethyldibenzylidenesorbitol.

The properties of the propylene copolymer compositions of the presentinvention are determined essentially by the glass transition temperatureof the propylene copolymers B. One way of determining the glasstransition temperature of the propylene copolymers B present in thepropylene copolymer compositions is examination of the propylenecopolymer compositions by means of DMTA (dynamic mechanical thermalanalysis), in which the deformation of a sample under the action of asinusoidally oscillating force is measured as a function of temperature.Here, both the amplitude and the phase shift of the deformation versusthe applied force are determined. Preferred propylene copolymercompositions have glass transition temperatures of the propylenecopolymers B in the range from −20° C. to −40° C., preferably from −25°C. to −38° C., particularly preferably from −28° C. to −35° C. and veryparticularly preferably from −31° C. to −34° C.

The glass transition temperature of the propylene copolymers B isdetermined essentially by their composition and especially by theproportion of copolymerized comonomers other than propylene. The glasstransition temperature of the propylene copolymers B can thus becontrolled via the type of monomers used in the polymerization of theproylene copolymers B and their ratios. For example, in the case ofpropylene copolymer compositions prepared using propylene-ethylenecopolymers as propylene copolymer B, an ethylene content of 16% byweight corresponds to a glass transition temperature of from −33° C. to−35° C.

The composition of the propylene copolymers B present in the propylenecopolymer compositions of the present invention is preferably uniform.This distinguishes them from conventional heterogeneous propylenecopolymers which are polymerized using Ziegler-Natta catalysts, sincethe use of Ziegler-Natta catalysts results in blockwise incorporation ofthe comonomer into the propylene copolymer even at low comonomerconcentrations, regardless of the polymerization process. For thepurposes of the present invention, the term “incorporated blockwise”indicates that two or more comonomer units follow one another directly.

In the case of preferred propylene copolymer compositions obtained frompropylene and ethylene, the structure of the propylene-ethylenecopolymers B can be determined by means of ¹³C-NMR spectroscopy.Evaluation of the spectrum is prior art and can be carried out by aperson skilled in the art using, for example, the method described by H.N. Cheng, Macromolecules 17 (1984), pp. 1950-1955 or L. Abis et al.,Makromol. Chemie 187 (1986), pp. 1877-1886. The structure can then bedescribed by the proportions of “PE_(x)” and of “PEP”, where PE_(x)refers to the propylene-ethylene units having ≧2 successive ethyleneunits and PEP refers to the propylene-ethylene units having an isolatedethylene unit between two propylene units. Preferred propylene copolymercompositions obtained from propylene and ethylene have a PEP/PE_(x)ratio of ≧0.75, preferably ≧0.85 and particularly preferably in therange from 0.85 to 2.5 and in particular in the range from 1.0 to 2.0.

Preference is also given to propylene copolymers B which have anisotactic structure with regard to subsequently incorporated propyleneunits.

The properties of the propylene copolymer compositions of the presentinvention are also determined by the viscosity ratio of the propylenecopolymer B and the propylene polymer A, i.e. the ratio of the molarmass of the dispersed phase to the molar mass of the matrix. Inparticular, this influences the transparency.

To determine the viscosity ratio, the propylene copolymer compositionscan be fractionated by means of TREF fractionation (Temperature RisingElution Fractionation). The propylene copolymer B is then the combinedfractions which are eluted by xylene at temperatures up to and including70° C. The propylene polymer A is obtained from the combined fractionswhich are eluted by xylene at temperatures above 70° C. The shearviscosity of the polymers is determined on the components obtained inthis way. The determination is usually carried out by a method based onISO 6721-10 using a rotation viscometer having a plate/plate geometry,diameter=25 mm, amplitude=0.05-0.5, preheating time=10-12 min, at atemperature of from 200 to 230° C. The ratio of the shear viscosity ofpropylene copolymer B to that of propylene polymer A is then reported ata shear rate of 100 s⁻¹.

In preferred propylene copolymer compositions, the ratio of the shearviscosity of propylene copolymer B to that of propylene polymer A at ashear rate of 100 s⁻¹ is in the range from 0.3 to 2.5, preferably from0.5 to 2 and particularly preferably in the range from 0.7 to 1.75.

The propylene copolymer compositions of the present invention preferablyhave a narrow molar mass distribution M_(w)/M_(n). The molar massdistribution M_(w)/M_(n) is, for the purposes of the invention, theratio of the weight average molar mass M_(w) to the number average molarmass M_(n). The molar mass distribution M_(w),M_(n) is preferably in therange from 1.5 to 3.5, particularly preferably in the range from 2 to2.5 and in particular in the range from 2 to 2.3.

The molar mass M_(n) of the propylene copolymer compositions of thepresent invention is preferably in the range from 20,000 g/mol to500,000 g/mol, particularly preferably in the range from 50,000 g/mol to200,000 g/mol and very particularly preferably in the range from 80,000g/mol to 150,000 g/mol.

The present invention further provides for the preparation of thepropylene polymers present in the propylene copolymer compositions ofthe present invention. This is preferably carried out in a multistagepolymerization process comprising at least two successive polymerizationsteps which are generally carried out in a reactor cascade. It ispossible to use the customary reactors employed for the preparation ofpropylene polymers.

The polymerization can be carried out in a known manner in bulk, insuspension, in the gas phase or in a supercritical medium. It can becarried out batchwise or preferably continuously. Solution processes,suspension processes, stirred gas-phase processes or gas-phasefluidized-bed processes are possible. As solvents or suspension media,it is possible to use inert hydrocarbons, for example isobutane, or elsethe monomers themselves. It is also possible to carry out one or moresteps of the process of the present invention in two or more reactors.The size of the reactors is not of critical importance for the processof the present invention. It depends on the output which is to beachieved in the individual reaction zone(s).

Preference is given to processes in which the polymerization in thesecond step in which the propylene copolymer(s) B is/are formed takesplace from the gas phase. The preceding polymerization of the propylenepolymers A can be carried out either in block, i.e. in liquid propyleneas suspension medium, or else from the gas phase. If all polymerizationstake place from the gas phase, they are preferably carried out in acascade comprising stirred gas-phase reactors which are connected inseries and in which the pulverulent reaction bed is kept in motion bymeans of a vertical stirrer. The reaction bed generally consists of thepolymer which is polymerized in the respective reactor. If the initialpolymerization of the propylene polymers A is carried out in bulk,preference is given to using a cascade made up of one or more loopreactors and one or more gas-phase fluidized-bed reactors. Thepreparation can also be carried out in a multizone reactor.

To prepare the propylene polymers present in the propylene copolymercompositions of the present invention, preference is given to usingcatalyst systems based on metallocene compounds of transition metals ofgroup 3, 4, 5 or 6 of the Periodic Table of the Elements.

Particular preference is given to catalyst systems based on metallocenecompounds of the formula (I),

where

-   M is zirconium, hafnium or titanium, preferably zirconium,-   X are identical or different and are each, independently of one    another, hydrogen or halogen or an —R, —R, —SO₂CF₃, —OCOR, —SR, —NR₂    or —PR₂ group, where R is linear or branched C₁-C₂₀-alkyl,    C₃-C₂₀-cycloalkyl which may be substituted by one or more    C₁-C₁₀-alkyl radicals, C₆-C₂₀-aryl, C₇-C₂₀-alkylaryl or    C₇-C₂₀-arylalkyl and may contain one or more heteroatoms of groups    13-17 of the Periodic Table of the Elements or one or more    unsaturated bonds, preferably C₁-C₁₀-alkyl such as methyl, ethyl,    n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl,    n-pentyl, n-hexyl, n-heptyl or n-octyl or C₃-C₂₀-cycloalkyl such as    cyclopentyl or cyclohexyl, where the two radicals X may also be    joined to one another and preferably form a C₄-C₄₀-dienyl ligand, in    particular a 1,3-dienyl ligand, or an —OR′O— group in which the    substituent R′ is a divalent group    -   selected from the group consisting of C₁-C₄₀-alkylidene,        C₆-C₄₀-arylidene, C₇-C₄₀-alkylarylidene and        C₇-C₄₀-arylalkylidene,    -   where X is preferably a halogen atom or an —R or —OR group or        the two radicals X form an —OR′O group and X is particularly        preferably chlorine or methyl,-   L is a divalent bridging group selected from the group consisting of    C₁-C₂₀-alkylidene radicals, C₃-C₂₀-cycloalkylidene radicals,    C₆-C₂₀-arylidene radicals, C₇-C₂₀-alkylarylidene radicals and    C₇-C₂₀-arylalkylidene radicals, which may contain heteroatoms of    groups 13-17 of the Periodic Table of the Elements, or a silylidene    group having up to 5 silicon atoms, e.g. —SiMe₂- or —SiPh₂-,    -   where L preferably is a radical selected from the group        consisting of —SiMe₂-, —SiPh₂-, —SiPhMe-, —SiMe(SiMe₃)-, —CH₂—,        —(CH₂)₂—, —(CH₂)₃— and —C(CH₃)₂—,-   R¹ is linear or branched C₁-C₂₀-alkyl, C₃-C₂₀-cycloalkyl which may    be substituted by one or more C₁-C₁₀-alkyl radicals, C₆-C₂₀-aryl,    C₇-C₂₀-alkylaryl or C₇-C₂₀-arylalkyl and may contain one or more    heteroatoms of groups 13-17 of the Periodic Table of the Elements or    one or more unsaturated bonds, where R¹ is preferably unbranched in    the a position and is preferably a linear or branched C₁-C₁₀-alkyl    group which is unbranched in the α position, in particular a linear    C₁-C₄-alkyl group such as methyl, ethyl, n-propyl or n-butyl,-   R² is a group of the formula —C(R³)₂R⁴ where-   R³ are identical or different and are each, independently of one    another, linear or branched C₁-C₂₀-alkyl, C₃-C₂₀-cycloalkyl which    may be substituted by one or more C₁-C₁₀-alkyl radicals,    C₆-C₂₀-aryl, C₇-C₂₀-alkylaryl or C₇-C₂₀-arylalkyl and may contain    one or more heteroatoms of groups 13-17 of the Periodic Table of the    Elements or one or more unsaturated bonds, or two radicals R³ may be    joined to form a saturated or unsaturated C₃-C₂₀-ring.    -   where R³ is preferably a linear or branched C₁-C₁₀-alkyl group,        and-   R⁴ is hydrogen or linear or branched C₁-C₂₀-alkyl, C₃-C₂₀-cycloalkyl    which may be substituted by one or more C₁-C₁₀-alkyl radicals,    C₆-C₂₀-aryl, C₇-C₂₀-alkylaryl or C₇-C₂₀-arylalkyl and may contain    one or more heteroatoms of groups 13-17 of the Periodic Table of the    Elements or one or more unsaturated bonds,    -   where R⁴ is preferably hydrogen,-   T and T′ are divalent groups of the formulae (II), (III), (IV), (V)    or (VI),    where    the atoms denoted by the symbols * and ** are joined to the atoms of    the compound of the formula (I) which are denoted by the same    symbol, and-   R⁵ are identical or different and are each, independently of one    another, hydrogen or halogen or linear or branched C₁-C₂₀-alkyl,    C₃-C₂₀-cycloalkyl which may be substituted by one or more    C₁-C₁₀-alkyl radicals, C₆-C₂₀-aryl, C₇-C₂₀-alkylaryl or    C₇-C₂₀-arylalkyl and may contain one or more heteroatoms of groups    13-17 of the Periodic Table of the Elements or one or more    unsaturated bonds,    -   where R⁵ is preferably hydrogen or a linear or branched        C₁-C₁₀-alkyl group, in particular a linear C₁-C₄-alkyl group        such as methyl, ethyl, n-propyl or n-butyl, and-   R⁶ are identical or different and are each, independently of one    another, halogen or linear or branched C₁-C₂₀-alkyl,    C₃-C₂₀-cycloalkyl which may be substituted by one or more    C₁-C₁₀-alkyl radicals, C₆-C₂₀-aryl, C₇-C₂₀-alkylaryl or    C₇-C₂₀-arylalkyl and may contain one or more heteroatoms of groups    13-17 of the Periodic Table of the Elements or one or more    unsaturated bonds,    -   where R⁶ is preferably an aryl group of the formula (VII),        where-   R⁷ are identical or different and are each, independently of one    another, hydrogen or halogen or linear or branched C₁-C₂₀-alkyl,    C₃-C₂₀-cycloalkyl which may be substituted by one or more    C₁-C₁₀-alkyl radicals, C₆-C₂₀-aryl, C₇-C₂₀-alkylaryl or    C₇-C₂₀-arylalkyl and may contain one or more heteroatoms of groups    13-17 of the Periodic Table of the Elements or one or more    unsaturated bonds, or two radicals R⁷ may be joined to form a    saturated or unsaturated C₃-C₂₀ ring,    -   where R⁷ is preferably a hydrogen atom, and-   R⁸ is hydrogen or halogen or linear or branched C₁-C₂₀-alkyl,    C₃-C₂₀-cycloalkyl which may be substituted by one or more    C₁-C₁₀-alkyl radicals, C₆-C₂₀-aryl, C₇-C₂₀-alkylaryl or    C₇-C₂₀-arylalkyl and may contain one or more heteroatoms of groups    13-17 of the Periodic Table of the Elements or one or more    unsaturated bonds,    -   where R⁸ is preferably a branched alkyl group of the formula        —C(R⁹)₃, where-   R⁹ are identical or different and are each, independently of one    another, a linear or branched C₁-C₆-alkyl group or two or three of    the radicals R⁹ are joined to form one or more ring systems.

It is preferred that at least one of the groups T and T′ is substitutedby a radical R⁶ of the formula (VII); it is particularly preferred thatboth groups are substituted by such a radical. Very particularpreference is given to at least one of the groups T and T′ being a groupof the formula (IV) which is substituted by a radical R⁶ of the formula(VII) and the other either has the formula (II) or (IV) and is likewisesubstituted by a radical R⁶ of the formula (VII).

The greatest preference is given to catalyst systems based onmetallocene compounds of the formula (VIII),

Particularly useful metallocene compounds and methods of preparing themare described, for example, in WO 01/48034 and the European patentapplication No. 01204624.9.

The metallocene compounds of the formula (I) are preferably used in therac or pseudorac form, where the pseudorac form is a complex in whichthe two groups T and T′ are in the rac arrangement relative to oneanother when all other substituents are disregarded. Such metallocenelead to polypropylenes having a predominantly isotactic structure.

It is also possible to use mixtures of various metallocene compounds ormixtures of various catalyst systems. However, preference is given tousing only one catalyst system comprising one metallocene compound,which is used for the polymerization of the propylene polymer A and thepropylene copolymer B.

Examples of useful metallocene compounds are

-   dimethylsilanediyl(2-ethyl-4-(4′-tert-butylphenyl)indenyl)(2-isopropyl-4-(4′-tert-butylphenyl)indenyl)zirconium    dichloride,-   dimethylsilanediyl(2-methyl-4-(4′-tert-butylphenyl)indenyl)(2-isopropyl-4-(1-naphthyl)indenyl)-zirconium    dichloride,-   dimethylsilanediyl(2-methyl-4-phenyl-1-indenyl)(2-isopropyl-4-(4′-tert-butylphenyl)-1-indenyl)-zirconium    dichloride,-   dimethylsilanediyl(2-methylthiapentenyl)(2-isopropyl-4-(4′-tert-butylphenyl)indenyl)zirconium    dichloride,-   dimethylsilanediyl(2-isopropyl-4-(4′-tert-butylphenyl)indenyl)(2-methyl-4,5-benzindenyl)zirconium    dichloride,-   dimethylsilanediyl(2-methyl-4-(4′-tert-butylphenyl)indenyl)(2-isopropyl-4-(4′-tert-butylphenyl)indenyl)zirconium    dichloride,-   dimethylsilanediyl(2-methyl-4-(4′-tert-butylphenyl)indenyl)(2-isopropyl-4-phenylindenyl)zirconium    dichloride,-   dimethylsilanediyl(2-ethyl-4-(4′-tert-butylphenyl)indenyl)(2-isopropyl-4-phenyl)indenyl)zirconium    dichloride and-   dimethylsilanediyl(2-isopropyl-4-(4′-tert-butylphenyl)indenyl)(2-methyl-4-(1-naphthyl)    indenyl)-zirconium dichloride    and mixtures thereof.

The preferred catalyst systems based on metallocene compounds generallyfurther comprise compounds capable of forming metallocenium ions ascocatalysts. Suitable compounds of this type include strong, unchargedLewis acids, ionic compounds having Lewis-acid cations and ioniccompounds containing Brönsted acids as cations. Examples aretris(pentafluorophenyl)borane, tetrakis(pentafluorophenyl)borate orsalts of N,N-dimethylanilinium. Likewise suitable as compounds capableof forming metallocenium ions and thus as cocatalysts are open-chain orcyclic aluminoxane compounds. These are usually prepared by reaction ofa trialkylaluminum with water and are generally in the form of mixturesof both linear and cyclic chain molecules of various lengths. Thepreferred catalyst systems based on metallocene compounds are usuallyused in supported form. Suitable supports are, for example, porousorganic or inorganic inert solids such as finely divided polymer powdersor inorganic oxides, for example silica gel. The metallocene catalystsystems may further comprise organometallic compounds of metals ofgroups 1, 2 and 13 of the Periodic Table, e.g. n-butyllithium oraluminum alkyls.

In the preparation of the propylene polymers present in the propylenecopolymer compositions of the present invention, preference is given tofirstly forming the propylene polymer A in a first step by polymerizingfrom 90% by weight to 100% by weight, based on the total weight of themixture, of propylene in the presence or absence of further olefins,usually at from 40° C. to 120° C. and pressures in the range from 0.5bar to 200 bar. The polymer obtainable by means of this reactionsubsequently has a mixture of from 2 to 95% by weight of propylene andfrom 5% to 98% by weight of further olefins polymerized onto it in asecond step, usually at from 40° C. to 120° C. and pressures in therange from 0.5 bar to 200 bar. The polymerization of the propylenepolymer A is preferably carried out at from 60 to 80° C., particularlypreferably from 65 to 75° C., and a pressure of from 5 to 100 bar,particularly preferably from 10 bar to 50 bar. The polymerization of thepropylene copolymer B is preferably carried out at from 60 to 80° C.,particularly preferably from 65 to 75° C., and a pressure of from 5 to100 bar, particularly preferably from 10 bar to 50 bar.

In the polymerization, it is possible to use customary additives, forexample molar mass regulators such as hydrogen or inert gases such asnitrogen or argon.

The amounts of the monomers added in the individual steps and also theprocess conditions such as pressure, temperature or the addition ofmolar mass regulators such as hydrogen is chosen so that the polymersformed have the desired properties. The scope of the invention includesthe technical teaching that a propylene copolymer composition which hasa good impact toughness at low temperatures and at the same time a goodtransparency and good stress whitening behavior is obtainable, forexample, by setting a defined comonomer content of the propylenecopolymer B and the viscosity ratio of propylene polymer A to propylenecopolymer B.

The composition of the propylene copolymer B has significant effects onthe transparency of the propylene copolymer compositions of the presentinvention. A reduction in the comonomer content of the propylenecopolymer B leads to an improved transparency, while at the same time,however, the low-temperature impact toughners decreases. An increase inthe comonomer content of the propylene copolymer B results in animprovement in the low-temperature impact toughness, but at the expenseof the transparency. At the same time, it is also possible to improvethe impact toughness by increasing the proportion of the propylenecopolymer B. Accordingly, the products of the present invention displayan advantageous combination of these properties, i.e. transparentproducts which at the same time have good low-temperature impacttoughness are obtained. In the case of the preferred use of ethylene ascomonomer, particular preference is given to setting an ethylene contentof the propylene copolymers B of from 10 to 20% by weight, in particularfrom 12 to 18% by weight and particularly preferably about 16% byweight. The transparency of the propylene copolymer compositions of thepresent invention is virtually independent of the proportion of thepropylene copolymer B present therein.

Adjustment of the viscosity ratio of propylene polymer A to propylenecopolymer B influences the dispersion of the propylene copolymer B inthe polymer matrix and thus has effects on the transparency of thepropylene copolymer compositions and on the mechanical properties.

The propylene copolymer compositions of the present invention display avery good impact toughness at low temperatures, which in addition iscombined with a good transparency and very good stress whiteningbehavior, and also a relatively high melting point, a high stiffness andgood heat distortion resistance. The propylene copolymer compositionsalso have low extractable contents, a homogeneous comonomer distributionand good organoleptics. Since the temperature for the brittle/toughtransition is below −15° C., the propylene copolymer compositions of thepresent invention can also be used in a temperature range which placeshigh demands on the material properties of the multiphase copolymers attemperatures below freezing point. This opens up wide-ranging newpossibilities for the use of the propylene copolymer compositions of thepresent invention in transparent applications in the low-temperaturerange.

The multiphase copolymers of the present invention are suitable forproducing fibers, films or moldings, in particular for producinginjection-molded parts, films, sheets or large hollow bodies, e.g. bymeans of injection-molding or extrusion processes. Possible applicationsare the fields of packaging, household articles, containers for storageand transport, office articles, electrical equipment, toys, laboratoryrequisites, motor vehicle components and gardening requisites, in eachcase especially for applications at low temperatures.

The invention is illustrated by the following preferred examples whichdo not restrict the scope of the invention:

EXAMPLES

The examples and comparative examples were carried out using proceduresanalogous to examples 98 to 102 of WO 01/48034, with comparativeexamples A, B and C corresponding to examples 98, 99 and 100 of WO01/48034.

Preparation of the Metallocene Catalyst

3 kg of Sylopol 948 were placed in a process filter whose filter platepointed downward and suspended in 15 l of toluene. 7 l of 30% strengthby weight MAO solution (from Albemarle) were metered in while stirringat such a rate that the internal temperature did not exceed 35° C. Afterstirring for a further 1 hour at a low stirrer speed, the suspension wasfiltered, firstly with no applied pressure and then under a nitrogenpressure of 3 bar. Parallel to the treatment of the support material,2.0 l of 30% strength by weight MAO solution were placed in a reactionvessel, 92.3 g ofrac-dimethylsilyl(2-methyl-4-(para-tert-butylphenyl)indenyl)(2-isopropyl-4-(para-tert-butylphenyl)indenyl)zirconiumdichloride were added, the solution was stirred for 1 hour and allowedto settle for a further 30 minutes. The solution was subsequently runonto the pretreated support material with the outlet closed. After theaddition was complete, the outlet was opened and the filtrate wasallowed to run off. The outlet was subsequently closed, the filter cakewas stirred for 15 minutes and allowed to stand for 1 hour. The liquidwas then pressed out from the filter cake by means of a nitrogenpressure of 3 bar with the outlet open. 15 l of isododecane were addedto the solid which remained, the mixture was stirred for 15 minutes andfiltered. The washing step was repeated and the filter cake wassubsequently pressed dry by means of a nitrogen pressure of 3 bar. Foruse in the polymerization, the total amount of the catalyst wasresuspended in 15 l of isododecane.

Polymerization

The process was carried out in two stirring autoclaves which wereconnected in series and each had a utilizable capacity of 200 l and wereequipped with a free-standing helical stirrer. Both reactors containedan agitated fixed bed of finely divided propylene polymer.

The propylene was passed in gaseous form into the first polymerizationreactor and polymerized at a mean residence time as shown in Table 1 bymeans of the metallocene catalyst at a pressure and temperature as shownin Table 1. The amount of metallocene catalyst metered in was such thatthe amount of polymer transferred from the first polymerization reactorinto the second polymerization reactor corresponded, on average, to theamounts shown in Table 1. The metallocene catalyst was metered intogether with the Frisch propylene added to regulate the pressure.Triethylaluminum in the form of a 1 molar solution in heptane waslikewise metered into the reactor.

The propylene copolymer obtained in the first gas-phase reactor wastransferred together with still active catalyst constituents into thesecond gas-phase reactor. There, the propylene-ethylene copolymer B waspolymerized onto it at a total pressure, a temperature and a meanresidence time as shown in Table 1. The ethylene concentration in thereaction gas was monitored by gas chromatography. The weight ratio ofthe propylene polymer A formed in the first reactor [A(I)] to thepropylene copolymer B formed in the second reactor [B(II)] is shown inTable 1. Isopropanol (in the form of a 0.5 molar solution in heptane)was likewise metered into the second reactor. The weight ratio of thepolymer formed in the first reactor to that formed in the second reactorwas controlled by means of isopropanol which was metered into the secondreactor in the form of a 0.5 molar solution in heptane and is shown inTable 1. To regulate the molar mass, hydrogen was metered into thesecond reactor as necessary. The proportion of propylene-ethylenecopolymer B formed in the second reactor is given by the difference ofamount transferred and amount discharged according to the relationship(output from second reactor−output from first reactor)/output fromsecond reactor. TABLE 1 Polymerization conditions Example ExampleComparative Comparative Comparative 1 2 example A example B example CReactor I Pressure [bar] 28 28 28 29 29 Temperature [° C.] 73.5 73 75 7575 Triethylaluminum, 1 M 90 90 60 60 60 in heptane [ml/h] Residence time[h] 1.5 1.5 2.25 2.25 2.25 Powder MFR (230° C./2.16 kg) 10.7 20 11.0 9.89.2 [g/10 min]/ISO 1133 Powder output [kg/h] 30 30 20 20 20 Reactor IIPressure [bar] 15 15 15 15 15 Temperature [° C.] 65 70 65 65 65 Ethylene[% by volume] 36 41.5 30 41 49 Hydrogen [standard l/h*] 10.6 0 0 0 0Residence time [h] 1.0 1.0 1.7 1.7 1.7 Powder output [kg/h] 43.7 42.624.1 24.2 24.3 Powder MFR (230° C./2.16 kg) 13 13 10.7 8.7 5.5[g/10min]/ISO 1133 Content of propylene 69 70 83 83 82 polymer A [% byweight] Content of propylene-ethylene 31 30 17 17 18 copolymer B [% byweight] Weight ratio of A(I):B(II) 2.2 2.4 4.9 4.8 4.7*Standard l/h: standard liters per hour

The polymer powder obtained in the polymerization was admixed with astandard additive mixture in the granulation step. Granulation wascarried out using a twin-screw extruder ZSK 30 from Werner & Pfleidererat a melt temperature of 250° C. The propylene copolymer compositionobtained contained 0.05% by weight of Irganox 1010 (from Ciba SpecialtyChemicals), 0.05% by weight of Irgafos 168, (from Ciba SpecialtyChemicals), 0.1% by weight of calcium stearate and 0.22% by weight ofMillad 3988 (bis-3,4-dimethylbenzylidenesorbitol, from MillikenChemical). The properties of the propylene copolymer composition areshown in Tables 2 and 3. The data were determined on the propylenecopolymer composition after addition of additives and granulation or ontest specimens produced therefrom. TABLE 2 Analytical results on thepropylene copolymer composition Example Example Comparative ComparativeComparative 1 2 example A example B example C C₂ content (¹³C-NMR) [% byweight] 5.7 6.2 2.7 5.1 10.2 C₂ content of propylene-ethylene 16.1 15.711.6 22.1 42.3 copolymer B (¹³C-NMR) [% by weight] Limiting viscosity(ISO 1628) [cm³/g] 160 148 175 164 185 Propylene polymer A 117 150 152157 191 Propylene-ethylene copolymer B PEP (¹³C-NMR) [% by weight] 3.973.94 1.5 1.7 1.7 PE_(x) (¹³C-NMR) [% by weight] 4.31 4.00 1.0 2.4 4.4PEP/PE_(x) 0.92 0.99 1.5 0.71 0.39 Glass transition temperatures [° C.]−2*/−35** −2*/−33** −6*** 2*/−42** 2*/−56** (DMTA, ISO 6721-7) Molarmass M_(n) [g/mol] 82 000 81 000 101 000 95 000 106 000 Molar massdistribution [M_(w)/M_(n)] 2.1 2.2 2.1 2.1 2.0 Shear viscosity η₁₀₀ ofpropylene- 162 311 293 382 1167 ethylene copolymer B**** Shear viscosityη₁₀₀ of propylene 353 182 313 377 404 polymer A**** Ratio of the shearviscosities of 0.5 1.7 0.9 1.0 2.9 propylene-ethylene copolymerB/propylene polymer A (ω = 100 s⁻¹)*****Glass transition temperature of the propylene polymer A**Glass transition temperature of the propylene-ethylene copolymer B***Only one value was measured. This value corresponds to a mixingtemperature and indicates that in the comparative example the propylenepolymer A and the propylene-ethylene copolymer B are miscible.****Shear viscosities at a shear rate of 100 s⁻¹ and a measurementtemperature of 230° C. in each case; except for example 1 in which themeasurement temperature was 220° C.

TABLE 3 Use-related tests on the propylene copolymer composition ExampleExample Comparative Comparative Comparative 1 2 example A example Bexample C MFR (230° C./2, 16 kg) [g/10 min]/ 16.2 16.5 12.3 8.7 6.9 ISO1133 DSC melting point [° C.]/ISO 3146 156.0 155.9 156 157.0 157.0 VicatA softening temperature [° C.]/ISO 128 127 141 139 140 306 VST/A50 Heatdistortion resistance HOT B 66 64 81 76 78 [° C.]/ISO 75-2 meth. BTensile E modulus [Mpa]/ISO 527 602 609 1156 1006 1093 Brittle/toughtransition temperature [° C.] −28 −23 9 −15 <−30 Charpy impact toughness(+23° C.) NF NF NF NF NF [kJ/m²]/ISO 179-2/1eU Charpy impact toughness(0° C.) 194 NF 163 NF NF [kJ/m²]/ISO 179-2/1eU Charpy impact toughness(−20° C.) 265 NF 28 180 130 [kJ/m²]/ISO 179-2/1eU Charpy notched impacttoughness 41.3 49.4 7.6 43.7 48.8 (+23° C.) [kJ/m²]/ISO 179-2/1eA.Charpy notched impact toughness (0° C.) 28.9 12.6 2.0 6.9 19.4[kJ/m²]/ISO 179-2/1eA Charpy notched impact toughness 2.6 2.1 1.4 1.53.3 (−20° C.) [kJ/m²]/ISO 179-2/1 eA Haze (1 mm*) [%]/ 15 25 12 35 68ASTM D 1003 Haze (50 μm**) [%] 15 17 10 20 17 ASTM D 1003 Stresswhitening (23° C.) [mm]/ 0 0 0 9.4 12.0 dome methodNF: no fracture*Injection-molded plates having a thickness of 1 mm.**Films having a thickness of 50 μm (no clear dependences of the hazevalue are observed)

Compared to comparative example A, the propylene copolymer compositionsaccording to the present invention have an improved toughness, inparticular at low temperatures. Compared to comparative example B and C,a significantly better transparency is achieved without the toughnessdeteriorating significantly.

Analysis

The production of the test specimens required for the use-related testsand the tests themselves were carried out in accordance with thestandards indicated in Table 3.

To determine analytical data on product fractions, the polymers orpolymer compositions prepared were fractionated by means of TREF asdescribed by L. Wild, “Temperature Rising Elution Fractionation”,Advanced Polym. Sci. 98, 1-47, 1990, in xylene. Fractions were eluted at40, 70, 80, 90, 95, 100, 110 and 125° C. and assigned to the propylenepolymer A prepared in reactor I or the propylene copolymer B prepared inreactor II. As propylene-ethylene copolymer B, use was made of thecombined fractions of a TREF eluted at temperatures up to and including70° C. As propylene polymer A, use was made of the combined fractions ofa TREF eluted above 70° C.

The brittle/tough transition was determined by means of the puncturetest described in ISO 6603-2/40/20/C/4.4. The velocity of the punch waschosen as 4.4 m/s, the diameter of the support ring was 40 mm and thediameter of the impact ring was 20 mm. The test specimen was clamped in.The test specimen geometry was 6 cm×6 cm at a thickness of 2 mm. Todetermine the temperature dependence curve, measurements were carriedout at steps of 2° C. in the temperature range from 26° C. to −35° C.using a test specimen preheated/precooled to the respective temperature.

In the present examples, the brittle/tough transition was determinedfrom the total deformation in mm defined as the displacement throughwhich the punch has traveled when the force has passed through a maximumand dropped to 3% of this maximum force. For the purposes of the presentinvention, the brittle/tough transition temperature is defined as thetemperature at which the total deformation is at least 25% below themean total deformation of the preceding 5 measurement points.

The determination of the Haze values was carried out in accordance withthe standard ASTM D 1003. The values were determined on samplescontaining 2200 ppm of Millad 3988. The test specimens wereinjection-molded plates having an edge length of 6×6 cm and a thicknessof 1 mm. The test specimens were injection molded at a melt temperatureof 250° C. and a tool surface temperature of 30° C. To determine thehaze value of films, films having a thickness of 50 μm were produced bypressing. After a storage time of 7 days at room temperature forafter-crystallization, the test specimens were clamped into the clampingdevice in front of the inlet orifice of a Hazegard System XL 211 fromPacific Scientific and the measurement was subsequently carried out.Testing was carried out at 23° C., with each test specimen beingexamined once in the middle. To obtain a mean, 5 test specimens weretested in each case.

The stress whitening behavior was assessed by means of the domed method.In the dome method, the stress whitening was determined by means of afalling dart apparatus as specified in DIN 53443 Part 1 using a fallingdart having a mass of 250 g, a punch diameter of 5 mm and a dome radiusof 25 mm. The drop was 50 cm. As test specimen, use was made of aninjection-molded circular disk having a diameter of 60 mm and athickness of 2 mm. The test specimen was injection molded at a melttemperature of 250° C. and a tool surface temperature of 30° C. Testingwas carried out at 23° C., with each test specimen being subjected toonly one impact test. The test specimen was first laid on a support ringwithout being clamped and the falling dart was subsequently released. Toobtain the mean, at least five test specimens were tested. The diameterof the visible stress whitening region is reported in mm and wasdetermined by measuring this region in the flow direction andperpendicular thereto on the side of the circular disk opposite that onwhich impact occurs and forming the mean of the two values.

The C₂ content and the structure of the propylene-ethylene copolymerswas determined by means of ¹³C-NMR spectroscopy.

The E modulus was measured in accordance with ISO 527-2: 1993. The testspecimen of type 1 having a total length of 150 mm and a parallelsection of 80 mm was injection molded at a melt temperature of 250° C.and a tool surface temperature of 30° C. To allow after-crystallizationto occur, the test specimen was stored for 7 days under standardconditions of 23° C./50% atmospheric humidity. A test unit model Z022from Zwick-Roell was used for testing. The displacement measurementsystem in the determination of the E modulus had a resolution of 1 μm.The testing velocity in the determination of the E modulus was 1 mm/min,otherwise 50 mm/min. The yield point in the determination of the Emodulus was in the range 0.05%-0.25%.

The determination of the melting point was carried out by means of DSC(differential scanning calorimetry). The measurement was carried out inaccordance with ISO standard 3146 using a first heating step at aheating rate of 20° C. per minute up to 200° C., a dynamiccrystallization at a cooled rate of 20° C. per minute down to 25° C. anda second heating step at a heating rate of 20° C. per minute back up to200° C. The melting point is then the temperature at which the enthalpyversus temperature curve measured during the second heating stepdisplays a maximum.

The determination of the molar mass M_(n) and the molar massdistribution M_(w)/M_(n) was carried out by gel permeationchromatography (GPC) at 145° C. in 1,2,4-trichlorobenzene using a GPCapparatus model 150C from Waters. The data were evaluated by means ofthe Win-GPC software from HS-Entwicklungsgesellschaft fürwissenschaftliche Hard-und Software mbH, Ober-Hilbersheim. The columnswere calibrated by means of polypropylene standards having molar massesfrom 100 to 10⁷ g/mol.

The determination of the limiting viscosity, namely the limiting valueof the viscosity number when the polymer concentration is extrapolatedto zero, was carried out in decalin at 135° C. in accordance with ISO1628.

The shear viscosities were determined by a method based on ISO 6721-10(RDS apparatus with plate/plate geometry, diameter=25 mm,amplitude=0.05-0.5, preheating time=10-12 min, T=200-230° C.). The ratioof the shear viscosity of propylene copolymer B to that of propylenecopolymer A was determined at a shear rate of 100 s⁻¹. The measurementtemperature was 220-230° C.

To determine the glass transition temperature by means of DMTA inaccordance with ISO 6721-7, a test specimen having dimensions of 10mm×60 mm and a thickness of 1 mm was stamped from a sheet pressed fromthe melt, 210° C., 7 min at 30 bar, cooling rate after completion ofpressing=15 K/min. This test specimen was clamped in the apparatus andthe measurement was commenced at −100° C. The heating rate was 2.5 K/minand the measurement frequency was 1 Hz.

1. A propylene copolymer composition comprising: A) a propylene polymercontaining from 0 to 10% by weight of olefins other than propylene andB) at least one propylene copolymer containing from 12 to 18% by weightof olefins other than propylene, where the propylene polymer A and thepropylene copolymer B are present as separate phases, the weight ratioof propylene polymer A to the propylene copolymer B is from 80:20 to60:40 and the propylene copolymer composition has a haze value of ≦30%,based on a path length of the propylene copolymer composition of 1 mm,and the brittle/tough transition temperature of the propylene copolymercomposition is ≦−15° C.
 2. The propylene copolymer composition asclaimed in claim 1, wherein the propylene polymer A is a propylenehomopolymer.
 3. The propylene copolymer composition as claimed in claim1 wherein the propylene polymer A has an isotactic structure.
 4. Thepropylene copolymer composition as claimed in claim 1, wherein theolefin other than propylene is exclusively ethylene.
 5. The propylenecopolymer composition as claimed in claim 1, wherein the value forstress whitening, determined by the dome method at 23° C., is from 0 to8 mm.
 6. (canceled)
 7. The propylene copolymer composition as claimed inclaim 1, wherein the copolymer B is dispersed in finely divided form inthe matrix A.
 8. (canceled)
 9. The propylene copolymer composition asclaimed in claim 1, comprising from 0.1 to 1% by weight, based on thetotal weight of the propylene copolymer composition, of a nucleatingagent.
 10. The propylene copolymer composition as claimed in claim 1,wherein a glass transition temperature of the propylene copolymer Bdetermined by means of DMTA (dynamic mechanical thermal analysis) is inthe range from −20° C. to −40° C.
 11. The propylene copolymercomposition as claimed in claim 1, wherein a ratio of the shearviscosity of propylene copolymer B to that of propylene polymer A at ashear rate of 100 s⁻¹ is in the range from 0.3 to 2.5.
 12. The propylenecopolymer composition as claimed in claim 1, wherein a molar massdistribution M_(w)/M_(n) is in the range from 1.5 to 3.5.
 13. A processfor preparing a propylene copolymer composition comprising: A) apropylene polymer containing from 0 to 10% by weight of olefins otherthan propylene and B) at least one propylene copolymer containing from12 to 18% by weight of olefins other than propylene, where the propylenepolymer A and the propylene copolymer B are present as separate phasesthe weight ratio of propylene polymer A to the propylene copolymer B isfrom 80:20 to 60:40 and the propylene copolymer composition has a hazevalue of ≦30%, based on a path length of the propylene copolymercomposition of 1 mm and the brittle/tough transition temperature of thepropylene copolymer composition is ≦−15° C.; the process comprisingpolymerizing monomers in a multistage polymerization with a catalystsystem based on metallocene compounds.
 14. A process comprisingproducing a fiber, film or molding from a propylene copolymercomposition comprising A) a propylene polymer containing from 0 to 10%by weight of olefins other than propylene and B) at least one propylenecopolymer containing from 12 to 18% by weight of olefins other thanpropylene, where the propylene polymer A and the propylene copolymer Bare present as separate phases, the weight ratio of propylene polymer Ato the propylene copolymer B is from 80:20 to 60:40 and the propylenecopolymer composition has a haze value of ≦30%, based on a path lengthof the propylene copolymer composition of 1 mm, and the brittle/toughtransition temperature of the propylene copolymer composition is ≦−15°C.
 15. A fiber, film or molding comprising a propylene copolymercomposition comprising: A) a propylene polymer containing from 0 to 10%by weight of olefins other than propylene and B) at least one propylenecopolymer containing from 12 to 18% by weight of olefins other thanpropylene. where the propylene polymer A and the propylene copolymer Bare present as separate phases, the weight ratio of propylene polymer Ato the propylene copolymer B is from 80:20 to 60:40 and the propylenecopolymer composition has a haze value of ≦30%, based on a path lengthof the propylene copolymer composition of 1 mm, and the brittle/toughtransition temperature of the propylene copolymer composition is ≦−15°C.